Field
The present disclosure relates to fireplaces, and more particularly, to the reduction of air pollutants from wood burning fireplace emissions.
Background
Recently, the quality of the air has become a serious concern worldwide. Significant effort has been directed to the minimization of various forms of pollutants in the air we breathe. For example, numerous regulatory standards have been imposed on automobile exhaust; many apartment houses no longer have incinerators for burning their tenants' waste; and large garbage burning incinerators must meet established standards or be shut down.
These concerns apply equally to the emissions from a common residential fireplace. Several of the compounds produced during the combustion of wood are of great concern. The problem of air pollution caused by the compounds produced when wood burns has been recognized by many, and a growing number of federal, state, and local environmental agencies are implementing regulations related to wood burning devices.
Emission standards for a majority of combustion processes, including wood burning fireplaces, have been established by the United States Environmental Protection Agency. The pollutants regulated by this agency are numerous and varied, including particles of organic compounds, carbon monoxide, volatile organic compounds, and nitrous oxides.
One simple fireplace pollutant removal device includes a filter, a fan, and a smoke detector. In operation, the filter is placed in the flue, and the fan is positioned above the filter to draw the exhaust gases up through the filter. The smoke detector is mounted in front of the fireplace. Here, the smoke detector acts as a monitor of gases reflected from a clogged filter and provides an alarm when the filter needs cleaning. A method of removing the clogged filter provides a roll of thin filter-paper which is scrolled through the flue as segments of the filter-paper saturate with pollutants. Unfortunately, because the filter paper may be combustible, this pollutant removal device may be a fire hazard. Assuming that a fire is not caused by overheating the filter paper, when the paper clogs smoke will be emitted from the fireplace into the area adjacent to the wood burning chamber, creating a smoke hazard.
Another conventional fireplace pollutant filter utilizes a ceramic fiber duct positioned along the path of the flow of combustion products, between the combustion chamber and the flue. Here, a first duct portion promotes secondary combustion of unburned products of combustion and a second duct portion directs products of combustion from the front of the combustion chamber to the flue. Though some pollutants may be removed by this device by the secondary combustion, many may still enter the atmosphere due to an incomplete removal by the secondary combustion and the lax of pollutant removal from the combustion products flowing through the second duct.
Still further improvement to the removal of pollutants from fireplace emissions has been achieved with the use of a reticulated foam structure having its surface coated with a catalytic material that converts pollutants into relatively harmless compounds. For example, U.S. Pat. No. 6,237,587, incorporated herein by reference in its entirety, discloses such a catalyst enabling improved airflow from the smoke chamber into the flue. Here, in order to quickly raise the temperature of the catalytic material to a suitable temperature where the cleaning of the exhaust may be improved, the catalytic material includes heaters embedded in the reticulated foam structure for heating the catalyst temperature when the fire is not hot enough to heat the catalyst itself to a suitable temperature to catalyze the exhaust compounds.
Although there are many catalytic devices designed to reduce pollutants in fluid streams such as fireplace smoke exhaust, the backpressures created by these devices are generally too high to allow proper fireplace operation. The increased backpressure may hinder the fireplace's draw, causing a variety of unacceptable consequences, including smoke escaping into the house instead of up the chimney.